HK1239935B - Systems and methods for intra-zone detection - Google Patents

Description

Systems and methods for in-region detection

Technical Field

The present invention generally relates to electronic article surveillance ("EAS") detection systems. More particularly, the present invention relates to systems and methods for implementing detection within an area.

Background Art

An EAS detection system generally includes an interrogation antenna for transmitting an electromagnetic signal into an interrogation zone; a tag that responds to the interrogation signal in some known electromagnetic manner; an antenna for detecting the tag's response; a signal analyzer for evaluating the signal generated by the detection antenna; and an alarm that indicates the presence of the tag within the interrogation zone. The alarm can then be the basis for initiating one or more appropriate responses based on the attributes of the facility. Typically, the interrogation zone is near an exit of a facility (such as a retail store), and the tag can be attached to merchandise, such as sales items or inventory items.

One type of EAS detection system utilizes acoustomagnetic (AM) tags. The general operation of an AM EAS detection system is described in U.S. Patent Nos. 4,510,489 and 4,510,490, the disclosures of which are incorporated herein by reference. Detecting tags in an AM EAS detection system using pedestals positioned at an exit has typically focused on detecting only tags within the pedestal spacing. However, the interrogation field generated by the pedestals can extend beyond the intended detection zone. For example, a first pedestal will typically include a primary antenna field directed toward a detection zone located between the first and second pedestals. When an exciter signal is applied to the first pedestal, the first pedestal will generate an electromagnetic field of sufficient strength to excite tags within the detection zone. Similarly, the second pedestal will typically include an antenna with a primary antenna field directed toward the detection zone (and toward the first pedestal). An exciter signal applied to the second pedestal will also generate an electromagnetic field of sufficient strength to excite tags within the detection zone. When the marker tag is excited in the detection zone, it will generate an electromagnetic signal, which can typically be detected by receiving the signal at antennas associated with the first and second bases.

AM EAS detection systems also include people counters to identify the zone a person is walking through, where a zone is defined as the space between two pedestals. This information is then used to trigger an alarm only in those areas where both an AM marker and a person are present. AM EAS systems can use the AM marker amplitude to estimate which pedestal the AM marker is closest to, but multiple pedestals or multiple marker sources reduce efficiency and make it impossible to determine which side of a pedestal the marker signal originates from. Adding a people counter can further limit specific zones by excluding other areas covered by a pedestal if no one is present.

Summary of the Invention

The present invention relates to a system and method for determining where an object or person is located within an EAS detection zone. The method includes synchronously transmitting a first signal from a first transmitter (e.g., a first infrared transmitter) and a second signal from a second transmitter (e.g., a second infrared transmitter). The first transmitter and the second transmitter are arranged on a first base of an EAS detection system so as to point toward the EAS detection zone. In some cases, the first signal includes a plurality of first signal bursts having a pulse width that is different from a pulse width of a plurality of second signal bursts of the second signal. Additionally or alternatively, each of the plurality of first signal bursts is transmitted by the first transmitter at a time different from a time at which the second transmitter transmits the second signal burst.

During a first time period, a first signal and a second signal are simultaneously detected by a first detector (e.g., a first infrared detector) and a second detector (e.g., a second infrared detector). The first and second detectors are disposed on a second base of the EAS detection system so as to point toward the EAS detection zone and are located opposite the first and second emitters, respectively. At a later time, a determination is made by a system controller or other electronic circuitry (e.g., electronic circuitry disposed within the base) as to where an object or person is located within the EAS detection zone based on a pattern of signals output by at least one of the first and second detectors, wherein the pattern reflects that at least one of the first and second signals was blocked by the object or person during at least one of the second and third time periods, wherein the object or person was traveling through the EAS detection zone during the at least one time period.

In some cases, when (1) the signal output by the first detector indicates that the first signal was blocked by the object or person during the second time period and the third time period; and (2) the signal output by the second detector indicates that the first infrared signal was blocked by the object or person during the third time period but not blocked during the second time period, the object or person is determined to be in the area closest to the first emitter and the second emitter in the multiple EAS detection zones. Alternatively or additionally, when (1) the signal output by the first detector indicates that the first signal was blocked by the object or person during the second time period but not blocked during the third time period; and (2) the signal output by the second detector indicates that the first signal was blocked by the object or person during the third time period but not blocked during the second time period, the object or person is determined to be in the area closest to the first emitter and the second emitter in the multiple EAS detection zones.

In those or other cases, when (1) the signal output by the first detector indicates that the first signal is blocked by the object or person during the second time period and the third time period, and the second signal is blocked by the object or person during the third time period and not blocked during the second time period; and (2) the signal output by the second detector indicates that both the first signal and the second signal are not blocked by the object or person during the second time period and the third time period, the object or person is determined to be in the area closest to the first detector and the second detector in the plurality of EAS detection zones. Alternatively or additionally, when (1) the signal output by the first detector indicates that the first signal is blocked by the object or person during the second time period, and the third signal is blocked by the object or person during the third time period; and (2) the signal output by the second detector indicates that both the first signal and the second signal are not blocked by the object or person during the second time period and the third time period, the object or person is determined to be in the area closest to the first detector and the second detector in the plurality of EAS detection zones.

In those or additional cases, when (1) the signal output by the first detector indicates that the second signal is blocked by the object or person; and (2) the signal output by the second detector simultaneously indicates that the first signal is blocked by the object or person, the object or person is determined to be within the central area of the EAS detection area. The location of the object or person within the EAS detection area can also be determined based on a time difference between signal changes in the signals output by at least one of the first detector and the second detector.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will be described with reference to the following drawings, wherein like reference numerals represent like items throughout the drawings, and in which:

FIG1 is a side view of an EAS detection system.

FIG. 2 is a top view of the EAS detection system in FIG. 1 , which may be used to understand the EAS detection area of the EAS detection system.

3 and 4 are diagrams useful for understanding the main field and rear field of antennas used in the EAS detection system of FIG. 1 .

FIG. 5 is a diagram useful for understanding detection areas in the EAS detection system of FIG. 1 .

6 is a graph showing infrared ("IR") signals emitted by two IR emitters and the signals output by two IR detectors when no beam interruption occurs during a given time period.

7 is a schematic diagram useful for understanding the operation of the system shown in FIG. 1 as an object or person travels through the EAS detection zone on the transmitter side of the EAS detection zone.

FIG. 8 is a diagram showing the signals output by two IR detectors in the situation presented in FIG. 7 .

9 is a schematic diagram useful in understanding the operation of the system shown in FIG. 1 as an object or person travels through an EAS detection zone on the transmitter side of the EAS detection zone.

FIG. 10 is a diagram showing the signals output by two IR detectors in the situation presented in FIG. 9 .

11 is a schematic diagram useful for understanding the operation of the system shown in FIG. 1 as an object or person travels through the detector side of an EAS detection area.

FIG. 12 is a diagram showing the signals output by two IR detectors in the situation presented in FIG. 11 .

13 is a schematic diagram useful for understanding the operation of the system shown in FIG. 1 as an object or person travels through the detector side of an EAS detection area.

FIG. 14 is a diagram showing the signals output by two IR detectors in the situation presented in FIG. 13 .

15 is a schematic diagram useful for understanding the operation of the system shown in FIG. 1 when an object or person travels through the center of an EAS detection zone.

FIG. 16 is a diagram showing the signals output by two IR detectors in the situation presented in FIG. 15 .

17 is a schematic diagram useful for understanding an algorithm for determining whether an object or person is located within the emitter side or the detector side of an EAS detection zone.

18 is a flow chart of an exemplary method for determining where an object or person is located within an Electronic Article Surveillance (EAS) detection zone.

DETAILED DESCRIPTION

It should be readily understood that the components of the embodiments generally described herein and illustrated in the accompanying drawings may be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the various embodiments illustrated in the accompanying drawings is not intended to limit the scope of the present disclosure, but rather is merely representative of various embodiments. Although various aspects of the embodiments are illustrated in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the present invention. The described embodiments are to be considered in all respects as illustrative only and not restrictive. The scope of the present invention is therefore indicated by the appended claims rather than by this detailed description. All changes that come within the meaning and range of equivalents of the claims are intended to be encompassed within the scope of the claims.

References to features, advantages, or similar language throughout this specification do not imply that all features and advantages that can be achieved with the present invention are or should be included in any single embodiment of the present invention. Rather, references to features and advantages are to be understood as meaning that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussions of features and advantages, and similar language throughout this specification, may, but do not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics of the present invention may be combined in any suitable manner in one or more embodiments. Based on the description herein, one skilled in the relevant art will recognize that the present invention may be practiced without one or more of the specific features or advantages of a particular embodiment. In other cases, it will be recognized that the additional features and advantages of certain embodiments may not be present in all embodiments of the present invention.

Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the indicated embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly indicates otherwise. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. As used in this document, the term "including" means "including, but not limited to."

As described above, conventional EAS systems use people counters to identify which zone a person is walking through. However, zone identification is limited to the space between the two pedestals of a conventional EAS system, without information about where within the zone a person is walking or which pedestal they are closest to. The present invention provides a solution to these shortcomings of conventional EAS systems. Furthermore, in the present invention, information about a person's location relative to the pedestals of the EAS system is used to identify specific pedestals to alert, dynamically change antenna settings, or eliminate alarms in areas where marker detection is not required (e.g., in the backfield of a pedestal). This will become more apparent as the discussion proceeds.

Referring now to Figures 1 and 2, an exemplary architecture of an EAS detection system 100 is provided. Note that the present invention is described herein in terms of an AMEAS detection system. However, the methods of the present invention may also be used with other types of EAS detection systems, including systems using radio frequency ("RF") type tags and radio frequency identification ("RFID") EAS detection systems.

The EAS detection system 100 is to be located adjacent to an entrance/exit 104 of a secure facility (e.g., a retail store). The EAS detection system 100 uses specially designed EAS marker tags ("security tags") that are applied to store merchandise or other items stored within the secure facility. The security tags can be deactivated or removed by authorized personnel at the secure facility. For example, in a retail environment, the security tags can be removed by store employees. When the EAS detection system 100 detects an active security tag 200 in an idealized representation of an EAS detection zone 150 proximate the entrance/exit, the EAS detection system will detect the presence of the security tag and will sound an alarm or generate some other appropriate EAS response. Thus, the EAS detection system 100 is arranged to detect and prevent the unauthorized removal of merchandise or products from a controlled area.

The EAS detection system 100 includes a pair of pedestals 102a, 102b, positioned a known distance apart (e.g., on opposite sides of an entrance/exit 104). Typically, the pedestals 102a, 102b are stabilized and supported by bases 106a, 106b. Generally, each pedestal 102a, 102b will include one or more antennas adapted to assist in detecting a particular EAS security tag, as described herein. For example, the pedestal 102a may include at least one antenna 302 adapted to transmit or generate an electromagnetic exciter signal field and receive response signals generated by security tags within the EAS detection zone 150. In some embodiments, the same antenna may be used for both receiving and transmitting functions. Similarly, the pedestal 102b may include at least one antenna 402 adapted to transmit or generate an electromagnetic exciter signal field and receive response signals generated by security tags within the EAS detection zone 150. The antennas provided in pedestals 102a, 102b can be conventional conductive coil or conductive wire loop designs, such as those commonly used in AM-type EAS pedestals. These antennas will sometimes be referred to herein as exciter coils. In some embodiments, a single antenna can be used in each pedestal. The single antenna is selectively coupled to the EAS receiver. The EAS transmitter is operated in a time-division multiplexed manner. However, as shown in FIG1 , it can be beneficial to include two antennas (or exciter coils) in each pedestal, with the upper antenna positioned above the lower antenna.

The antennas located in the pedestals 102a, 102b are electrically coupled to a system controller 190. The system controller 190 controls the operation of the EAS detection system 100 to perform the EAS functions as described herein. The system controller 190 can be located within the base 106a, 106b of one of the pedestals 102a, 102b, or can be located within a separate chassis at a location near the pedestal. For example, the system controller 190 can be located in a ceiling that is directly above or adjacent to the pedestals 102a, 102b.

As described above, the EAS detection system comprises an AM-type EAS detection system. Thus, each antenna is used to generate an electromagnetic ("EM") field that serves as a security tag exciter signal. The security tag exciter signal causes a strip (e.g., a strip formed of a magnetostrictive or ferromagnetic amorphous metal) contained within a security tag within the EAS detection zone 150 to mechanically oscillate. Due to the excitation signal, the security tag will resonate and mechanically vibrate due to the magnetostrictive effect. This vibration will continue for a short time after the excitation signal ceases. The vibration of the strip causes its magnetic field to change, which can induce an AC signal in the receiver antenna. This induced signal is used to indicate the presence of the strip within the EAS detection zone 150. As described above, the same antenna contained in bases 102a, 102b can serve as both a transmitting antenna and a receiving antenna. Thus, the antenna in each of bases 102a, 102b can be used to detect the security tag exciter signal in several different modes. These modes are described in more detail below.

Referring now to Figures 3 and 4, exemplary antenna field patterns 300, 400 of antennas 302, 402 included in bases 102a, 102b are shown. As is known in the art, an antenna radiation pattern is a graphical representation of how the radiation (or reception) properties of a given antenna vary with spacing. The properties of the antenna are the same in both the transmit and receive modes of operation. As such, the antenna radiation patterns shown are applicable to both transmit and receive operations as described herein. The exemplary antenna field patterns 300, 400 shown in Figures 3-4 are azimuth plane patterns, representing antenna patterns in the x, y coordinate plane. The azimuth patterns are represented in polar coordinate form and are sufficient for understanding the inventive arrangement. The azimuth antenna field patterns shown in Figures 3-4 are a useful way to visualize the directions in which antennas 302, 402 will transmit and receive signals at a particular transmitter power level.

The antenna field pattern 300 shown in FIG3 includes a main lobe 304 peaking at φ and a backfield lobe 306 peaking at angle φ. Conversely, the antenna field pattern 400 shown in FIG4 includes a main lobe 404 peaking at φ and a backfield lobe 406 peaking at angle φ. In the EAS detection system 100, each pedestal 102a, 102b is positioned so that the main lobe of the antenna contained therein is directed into the EAS detection zone 150. Consequently, a pair of pedestals 102a, 102b in the EAS detection system 100 will produce overlap in the antenna field patterns 300, 400, as shown in FIG5. Note that the antenna field patterns 300, 400 shown in FIG5 are scaled for purposes of understanding the present invention. In particular, the patterns illustrate the outer boundaries or limits of the region in which an exciter signal of a particular amplitude applied to the antennas 302, 402 will produce a detectable response in the EAS security tag. However, it should be understood that a security tag within the confines of at least one antenna field pattern 300, 400 will produce a detectable response when stimulated by the stimulator signal.

The overlapping antenna field patterns 300 and 400 in FIG5 will include region A, where main lobes 304 and 404 overlap. However, as can be observed in FIG5 , there can also be some overlap between the main lobe of each pedestal and the backfield lobes associated with the other pedestals. For example, it can be observed that in region B, main lobe 404 overlaps with backfield lobe 306. Similarly, in region C, main lobe 304 overlaps with backfield lobe 306. Region A between pedestals 102a and 102b defines EAS detection zone 150, within which active security tags should cause EAS detection system 100 to generate an alarm response. Security tags in region A are stimulated by the energy associated with the exciter signal within main lobes 304 and 404 and will generate a response detectable at each antenna. The response generated by security tags in region A is detected within the main lobe of each antenna and processed in system controller 190. Note that security tags in regions B or C will also be stimulated by antennas 302 and 402. The response signals generated by the security tags in these regions B and C will also be received at one or both antennas. This response signal is referred to herein as the "security tag signal."

Referring again to Figures 1-2, at least two IR emitters 108, 202 are disposed on base 102a. At least two IR detectors 110, 204 are disposed on base 102b, directly opposite emitters 108, 202, respectively. IR emitters and detectors are well known in the art and will not be described herein. Any known or future IR emitter and/or IR detector can be used herein without limitation. Furthermore, the present invention is not limited to IR emitters and detectors. Other emitter/detector configurations can also be used herein.

The IR emitters and detectors are arranged to point toward the EAS detection area 150. As such, the IR emitters and detectors facilitate detection of objects and persons moving through the EAS detection area 150. In this regard, both IR detectors 110 and 204 detect the IR beams emitted by both IR emitters 108 and 202. Additionally, other IR emitters and detectors may also be used to increase detection of objects and persons outside of the EAS detection area 150. In this case, the additional IR emitters and detectors may be arranged outside of the EAS detection area 150.

Although only two IR emitters and IR detectors are shown in Figures 1-2, the present invention is not limited thereto. Any number of IR emitters and IR detectors suitable for a particular application may be employed in the present invention. For example, multiple IR emitters may be arranged along the entire width of base 102a. Similarly, multiple IR detectors can be arranged along the entire width of base 102b. In all cases, each adjacent pair of IR emitters is spaced the same or a different distance from another adjacent pair of IR emitters. Similarly, each adjacent pair of IR detectors is spaced the same or a different distance from another adjacent pair of IR detectors.

Additionally, each IR emitter and IR detector is shown as being located at a specific distance 160 from a floor 170. Distance 160 can have any value selected based on the specific application. For example, distance 160 was selected to be 53 inches, which is considered to be the optimal height for detecting beam interruptions caused by a person. This height ensures that a child will not cause a beam interruption and also ensures that errors related to moving limbs will not occur. The present invention is not limited to the details of this example.

The IR emitters and detectors provide a means for detecting beam breaks caused by an object or person moving through the EAS detection zone 150 established between the bases 102a, 102b. As the object or person moves through the EAS detection zone 150, the object or person blocks the IR beams emitted by the IR detectors 108, 202 in a specific order. Depending on which side of the EAS detection zone 150 the beam break occurs, the output beam break information generated by the IR detectors 110, 204 will be different. For example, a person walking in direction y on the emitter side 206 of the EAS detection zone 150 will cause the IR detector 110 to detect a beam break in the IR beam emitted by the IR emitter 108, followed by another IR detector 204 detecting a beam break in the IR beam emitted by the same IR emitter 108. Conversely, a person walking on the detector side 208 of the EAS detection zone 150 will cause the IR detector 110 to detect a beam break in the IR beam emitted by IR emitter 108, and subsequently, the same IR detector 110 will detect a beam break in the IR beam emitted by IR emitter 202. A person walking through the center 210 of the EAS detection zone 150 in direction y will cause beam breaks in the IR beams emitted by both IR emitters 108, 202. More specifically, the IR detector 110 will detect a beam break in the IR beam emitted by IR emitter 202, while the IR detector 204 will detect a beam break in the IR beam emitted by IR emitter 108.

An algorithm implemented in the system controller 190 (or other electronic circuitry of the pedestal) uses the beam interruption sequence information to (1) detect objects and people moving through the EAS detection area 150, (2) determine the direction of movement of an object or person moving through the EAS detection area 150, and (3) determine which side of the EAS detection area 150 the object or person is traveling through. By recognizing specific beam interruption patterns, the algorithm can determine whether a person is walking through the EAS detection area 150 on the emitter side 206, the detector side 208, or the center 210 of the EAS detection area 150. Analysis of the timing between beam interruptions is also used to estimate the distance of an object or person from a given pedestal 102a, 102b. The manner in which the detection/determination and distance estimation of (1)-(3) are accomplished will become apparent as the discussion proceeds.

6, a diagram 600 is provided that can be used to understand the operation of the system 100 when no beam interruption occurs during a given time period. Thus, diagram 600 schematically illustrates IR signals 604, 606 transmitted by IR emitters 108, 202 and signals 602, 608 output from IR detectors 110, 204 as a result of IR detectors 110, 204 receiving both transmitted IR signals 604, 606. The transmitted IR signal 604 is shown as comprising time-division multiplexed ("TDM") bursts having a frequency of N kHz (e.g., 38 kHz) and a pulse width 614 of M us (e.g., 900 µs). The transmitted IR signal 606 is shown as comprising TDM bursts having a frequency of N kHz (e.g., 38 kHz) and a pulse width 616 of X us (e.g., 500 µs). Each TDM burst 618 of IR signal 604 is offset in time relative to an adjacent TDM burst 620 of IR signal 606. For the transmitted IR signal, the present invention is not limited to TDM-based burst technology. Other technologies using different modulation frequencies, different wavelengths, different pulse widths and different data stream transmissions can also be used.

In FIG6 , the two output signals 602 and 608 are identical because both IR signals 604 and 606 are received at both IR detectors 110 and 204. The output of each IR detector 110 and 204 is statically high. Thus, when the IR detector receives the transmitted IR signal burst, the signal output by the IR detector transitions from its statically high state to a low state. A relatively short time delay 614 occurs between the time a TDM burst 618 of IR signal 604 is transmitted by IR transmitter 108 and the time the state of either signal 602 or 608 changes to its low state in response to receiving TDM burst 618 at IR detector 110 or 204. Similarly, a time delay 616 occurs between the time a TDM burst 620 of IR signal 606 is transmitted by IR transmitter 202 and the time the state of either signal 602 or 608 changes to its low state in response to receiving TDM burst 620 at IR detector 110 or 204.

The two signals 602, 608 are provided by the IR detectors 110, 204 to the system controller 190 for processing. When the two signals 602, 608 indicate that both IR signals 604, 606 are being received at both IR detectors 110, 204, the system controller 190 determines that no object or person is traveling through the EAS detection zone 150. In some cases, the system controller 190 will not take any subsequent control measures in response to this determination.

Various scenarios will now be described with reference to Figures 7-17. In each scenario, an object or person is traveling through EAS detection zone 150 in a particular direction (e.g., the y-direction). The present invention is not limited thereto. The reader should readily appreciate that the object or person may be traveling through EAS detection zone 150 in the opposite direction. In such scenarios, the specific order in which beam interruptions occur relative to IR emitters 108, 202 may vary depending on each specific scenario. These beam interruption sequence variations will become apparent to the reader as the discussion proceeds.

7, a schematic diagram is provided that can be used to understand the situation where an object or person 702 is traveling through the EAS detection zone 150 on the transmitter side 206. As shown in FIG7, the object or person 702 is traveling in the y-direction. Before the person enters the EAS detection zone 150, the two signals output by the IR detectors 110, 204 are the same as those shown in FIG6.

Note that when the IR signal 604 transmitted by the emitter 108 is blocked at the IR detector 110 before the IR signal 604 transmitted by the emitter 108 is blocked at the IR detector 204, the beam interruption pattern may indicate that a person or object is on the emitter side 206 of the EAS detection zone 150. This will become more apparent as the discussion proceeds.

As the object or person enters the EAS detection zone, the object or person 702 first causes a beam break in the IR signal 604 transmitted by the IR emitter 108, but does not cause a beam break in the IR signal 606 transmitted by the IR emitter 202. The beam break in the IR signal 604 is detected by the IR detector 110, but not by the IR detector 204. In fact, during the time period when the object or person 702 is in the first position 706, the IR detector 110 only receives the TDM burst 620 from the IR emitter 202, thereby detecting the beam break in the IR signal 604 transmitted by the IR emitter 108. In contrast, the IR detector 204 receives the TDM bursts 618, 620 from both the IR emitters 108, 202 during this time period.

If the object or person 702 continues to enter the EAS detection zone 150, the object or person 702 will next cause a beam break in the IR signal 604, which will be detected by both the IR detectors 110 and 204. At this point, during the time period that the object or person 702 is in the second position 708, both the IR detectors 110, 204 receive only the TDM bursts 620 from the IR emitter 202, and thus both the IR detectors 110, 204 detect the beam break in the IR signal 604 transmitted by the IR emitter 108.

A diagram 800 illustrating the signals 802, 808 output by the IR detectors 110, 204 in the situation presented in Figure 7 is provided in Figure 8. As shown in Figure 8, both IR signals 604, 606 are received at both IR detectors 110, 204 during a first time period 802. The first time period is when the object or person 702 has not yet caused a beam interruption to occur.

During the second time period 804, the object or person 702 is in its first position 706. As such, a beam interruption occurs with respect to the IR signal 604 transmitted by the IR emitter 108. In effect, the IR detector 110 receives only the IR signal 606 transmitted by the IR emitter 202 during the second time period 804. However, the IR detector 204 continues to receive the IR signals 604 and 606 from both IR emitters 108, 202.

During the third time period 806, the object or person 702 is in its second position 708. As such, a beam interruption occurs with respect to the IR signal 604 emitted by the IR emitter 108. Consequently, both IR detectors 110, 204 receive only the IR signal 606 from the IR emitter 202 during the third time period 806.

The two output signals 802, 808 are provided by the IR detectors 110, 204 to the system controller 190 for processing. When the combined IR signals 802, 808 have the beam interruption pattern shown in FIG8 , that is, when (1) the combined IR signal 802 indicates that only the IR signal 606 is being received by the IR detector 110 during the second and third time periods, and (2) the combined IR signal 808 indicates that only the IR signal 606 is being received by the IR detector 204 during the third time period, the system controller 190 determines that an object or person is traveling through the transmitter side 206 of the EAS detection zone 150.

In some cases, the system controller 190 will take subsequent control measures in response to this determination. For example, the system controller 190 can perform actions to appropriately alert the correct pedestals of the EAS detection system. When a person walks through the EAS detection area 150 with an active security tag, both pedestals 102a and 102b detect the presence of the active security tag. In conventional EAS detection systems, visual and/or audible alarms are sounded on both pedestals 102a and 102b. This is undesirable in some cases. Therefore, in the present invention, the system controller 190 determines whether a person is walking through the transmitter side, center side, or detector side of the EAS detection area based on the signals output by the IR detectors 110, 204. Based on the results of this determination, the system controller 190 will perform actions so that only one or more alarms of the pedestal closest to the person are sounded. As a result, the EAS detection system of the present invention provides store employees with clear indications of: (1) which area within the EAS detection area the person is walking through, and/or (2) which EAS detection area among multiple adjacent EAS detection areas the person is walking through. In effect, store associates can make more informed decisions regarding which of multiple individuals traveling through one or more EAS detection zones actually possesses an active security tag.

Additionally or alternatively, system controller 190 can use the results of this determination to dynamically modify (e.g., reduce) the strength of the antenna radiation field of the pedestals. This dynamic modification has certain advantages, such as saving battery power. For example, if the determination indicates that a person is traveling through the transmitter side of the EAS detection area, the strength of the antenna radiation field emitted by pedestal 102a is dynamically reduced. Similarly, if the determination indicates that a person is traveling through the detector side of the EAS detection area, the strength of the antenna radiation field emitted by pedestal 102b is dynamically reduced. If the determination indicates that a person is traveling through the center of the EAS detection area, the strength of the antenna radiation field emitted by both pedestals 102a and 102b is changed.

System controller 190 can also use the results of this determination to prevent an alarm from being issued if certain conditions are met. For example, consider a first scenario: both pedestals 102a and 102b detect a security tag in their vicinity, but the IR detector's output signals indicate that a person is not within the EAS detection zone. In this case, issuing a pedestal alarm is prevented because the person is likely behind the pedestals. Now consider a second scenario: both pedestals 102a and 102b detect a security tag in their vicinity, but the IR detector's output signals indicate that a person is entering the facility. In this case, issuing a pedestal alarm is also prevented because an alarm only needs to be issued for persons exiting the facility. The present invention is not limited to the details of these two examples. For example, the emitter and detector can be positioned outside the EAS detection zone and can operably work in conjunction with the emitter/detector disposed on pedestals 102a and 102b to suppress alarms issued by security tags located behind the pedestals (e.g., within areas B and C in FIG. 5 ).

9, a schematic diagram is provided that can be used to understand another scenario in which an object or person 902 is traveling through the EAS detection zone 150 on the transmitter side 206. As shown in FIG9, the object or person 902 is traveling in the y-direction. Before the person enters the EAS detection zone 150, the two signals output by the IR detectors 110, 204 are the same as those shown in FIG6.

Note that when the IR signal 604 transmitted by the emitter 108 is blocked at the IR detector 110 before the IR signal 604 transmitted by the emitter 108 is blocked at the IR detector 204, the beam interruption pattern may indicate that a person or object is on the emitter side 206 of the EAS detection zone 150. This will become more apparent as the discussion proceeds.

As the object or person enters the EAS detection zone, the object or person 902 first causes a beam break in the IR signal 604 transmitted by the IR emitter 108, but does not cause a beam break in the IR signal 606 transmitted by the IR emitter 202. This beam break is detected by the IR detector 110, but not by the IR detector 204. In fact, during the time period when the object or person 902 is in the first position 906, the IR detector 110 only receives the TDM burst 620 from the IR emitter 202, thereby detecting the beam break in the IR signal 604 transmitted by the IR emitter 108. In contrast, the IR detector 204 receives the TDM bursts 618, 620 from both IR emitters 108, 202 during this time period.

If the object or person 902 continues to enter the EAS detection zone 150, the object or person 902 will continue to cause beam breaks in the IR signal 604. However, the beam breaks will not be detected by the IR detector 110, but only by the IR detector 204. At this point, the IR detector 110 receives the TDM bursts 618, 620 from both the IR emitters 108 and 202, while the IR detector 204 receives the TDM bursts 620 only from the IR emitter 202.

A graph 1000 illustrating the signals 1002, 1008 output by the IR detectors 110, 204 in the situation presented in Figure 9 is provided in Figure 10. As shown in Figure 10, during a first time period 1002, both IR signals 604, 606 are received at both IR detectors 110, 204. The first time period is when the object or person 902 has not yet caused a beam interruption to occur.

During the second time period 1004, the object or person 902 is in its first position 906. As such, a beam interruption occurs with respect to the IR signal 604 transmitted by the IR emitter 108. In effect, the IR detector 110 receives only the IR signal 606 from the IR emitter 202 during the second time period 1004. However, the IR detector 204 continues to receive both IR signals 604 and 606 from the IR emitters 108, 202.

Note that in some cases, IR detector 110 may receive TDM bursts from both IR transmitters 108 and 202 before the beam break of IR signal 604 is detected by IR detector 204. In this case, signal 1002 would show that both IR signals 604 and 606 are being received by IR detector 110 at the end of second time period 1004.

During the third time period 1006, the object or person 902 is in its second position 908. As such, a beam interruption occurs with respect to the IR signal 604 transmitted by the IR emitter 108. However, this beam interruption will not be detected by the IR detector 110, but only by the IR detector 204. Consequently, the signal 1002 output by the IR detector 110 has the same shape and characteristics as the signal it output during the first time period 1002. In contrast, the shape of the signal 1008 output by the IR detector 204 indicates that the IR detector 204 was only receiving the TDM burst 620 during the third time period 1006.

The two signals 1002, 1008 are provided by the IR detectors 110, 204 to the system controller 190 for processing. When the signals 1002, 1008 have the beam interruption pattern shown in FIG10, that is, when (1) the signals 1002, 1008 indicate that both IR signals 604, 606 were received by the IR detectors 110, 204 during the first time period 1002, (2) the signal 1002 indicates that the IR signal 604 was not received by the IR detector 110 during the second time period 1004, and (3) the signal 1008 indicates that the IR signal 604 was not received by the IR detector 204 during the third time period 1006, the system controller 190 determines that an object or person is traveling through the transmitter side 206 of the EAS detection zone 150. In some cases, the system controller 190 will take subsequent control measures in response to this determination. The subsequent control measures are the same or similar to those described above with respect to FIG8.

11, a schematic diagram is provided that can be used to understand the situation where an object or person 1102 is traveling through the EAS detection zone 150 on the detector side 208. As shown in FIG11, the object or person 1102 is traveling in the y-direction. Before the person enters the EAS detection zone 150, the two signals output by the IR detectors 110, 204 are the same as those shown in FIG6.

Note that when the IR signal transmitted by IR emitter 108 is blocked at IR detector 110 before the IR signal transmitted by non-adjacent emitter 202 is blocked at IR detector 110, the beam interruption pattern may indicate that a person or object is located to the side of the detector. This will become more apparent as the discussion proceeds.

As the object or person enters the EAS detection zone 150, the object or person 1102 first causes a beam break in the IR signal 604 transmitted by the IR emitter 108, but does not cause a beam break in the IR signal 606 transmitted by the IR emitter 202. This beam break is detected by the IR detector 110, but not by the IR detector 204. In fact, during the time period that the object or person 1102 is in the first position 1106, the IR detector 110 only receives the TDM burst 620 from the IR emitter 202, thereby detecting the beam break in the IR signal 604 transmitted by the IR emitter 108. In contrast, the IR detector 204 receives the TDM bursts 618, 620 from both IR emitters 108, 202 during this time period.

If the object or person 1102 continues to enter the EAS detection zone 150, the object or person 1102 will next cause a beam break of the IR signal 606, which will also be detected by the IR detector 110. At this point, during the time period that the object or person 1102 is in the second position 1108, the IR detector 110 does not receive any TDM bursts 618, 620 from both IR emitters 108, 202, and thus the IR detector 110 detects the simultaneous beam break of the IR signals 604, 606 transmitted by the IR emitters 108, 202. Note that during this time period, the IR detector 204 continues to receive TDM bursts 618, 620 from both IR emitters 108, 202.

A diagram 1200 illustrating the signals 1202, 1208 output by the IR detectors 110, 204 in the scenario presented in Figure 11 is provided in Figure 12. As shown in Figure 12, both IR signals 604, 606 are received at both IR detectors 110, 204 during a first time period 1202. The first time period is when an object or person 1102 has not yet caused a light beam interruption to occur.

During the second time period 1204, the object or person 1102 is in its first position 1106. As such, a beam interruption occurs with respect to the IR signal 604 transmitted by the IR emitter 108. In effect, the IR detector 110 receives only the IR signal 606 from the IR emitter 202 during the second time period 1204. However, the IR detector 204 continues to receive the IR signals 604 and 606 from both the IR emitters 108, 202.

During the third time period 1206, the object or person 1102 is in its second position 1108. As such, a beam interruption also occurs with respect to the IR signal 606 emitted by the IR emitter 202. Consequently, the IR detector 110 does not receive any IR signals 604, 606 and thus remains at its high quiescent state during the third time period 1206. Note that the IR detector 204 receives both IR signals 604, 606 during all time periods 1202-1206.

The two signals 1202, 1208 are provided by the IR detectors 110, 204 to the system controller 190 for processing. When the signals 1202, 1208 have the beam interruption pattern shown in FIG12, that is, when (1) the signal 1202 indicates that both IR signals 604, 606 are being received by the IR detector 110 during the first time period, (2) the signal 1202 indicates that only the IR signal 606 is being received by the IR detector 110 during the second time period, (3) the signal 1202 indicates that neither IR signals 604, 606 are being received by the IR detector 110 during the third time period, and (4) the IR signal 1208 indicates that both IR signals 604, 606 are being received by the IR detector 204 during all three time periods, the system controller 190 determines that an object or person has traveled past the detector side 208 within the EAS detection zone 150. In some cases, the system controller 190 will take subsequent control measures in response to this determination. Subsequent control measures are the same or similar to those described above with respect to FIG. 8 .

13, a schematic diagram is provided that can be used to understand another situation in which an object or person 1302 is traveling through the EAS detection zone 150 on the detector side 208. As shown in FIG13, the object or person 1302 is traveling in the y-direction. Before the person enters the EAS detection zone 150, the two signals output by the IR detectors 110, 204 are the same as those shown in FIG6.

Note that when the IR signal transmitted by IR emitter 108 is blocked at IR detector 110 before the IR signal transmitted by IR emitter 108 is blocked at IR detector 204, the beam interruption pattern can indicate that a person or object is located on the detector side. This will become more apparent as the discussion proceeds.

As the object or person enters the EAS detection zone 150, the object or person 1302 first causes a beam break in the IR signal 604 transmitted by the IR emitter 108, but does not cause a beam break in the IR signal 606 transmitted by the IR emitter 202. This beam break is detected by the IR detector 110, but not by the IR detector 204. In fact, during the time period that the object or person 1302 is in the first position 1306, the IR detector 110 only receives the TDM burst 620 from the IR emitter 202, thereby detecting the beam break in the IR signal 604 transmitted by the IR emitter 108. In contrast, the IR detector 204 receives the TDM bursts 618, 620 from both IR emitters 108, 202 during this time period.

If the object or person 1302 continues to enter the EAS detection zone 150, the object or person 1302 will next cause a beam break in the IR signal 606 to be detected by the IR detector 110. At this time, during the time period when the object or person 1302 is in the second position 1308, the IR detector 110 receives the TDM burst 618 from the IR emitter 108 instead of the TDM burst 620 from the IR emitter 202, thereby detecting the beam break in the IR signal 606 transmitted by the IR emitter 202. Note that during this time period, the IR detector 204 continues to receive the TDM bursts 618, 620 from both the IR emitters 108, 202.

A diagram 1400 illustrating the signals 1402, 1408 output by the IR detectors 110, 204 in the situation presented in Figure 13 is provided in Figure 14. As shown in Figure 14, both IR signals 604, 606 are received at both IR detectors 110, 204 during a first time period 1402. The first time period is when the object or person 1302 has not yet caused a beam interruption to occur.

During the second time period 1404, the object or person 1302 is in its first position 1306. As such, a beam interruption occurs with respect to the IR signal 604 transmitted by the IR emitter 108. In effect, during the second time period 1404, the IR detector 110 only receives the IR signal 606 from the IR emitter 202. However, the IR detector 204 continues to receive the IR signals 604 and 606 from both the IR emitters 108, 202.

During the third time period 1406, the object or person 1302 is in its second position 1308. As such, a beam interruption occurs with respect to the IR signal 606 transmitted by the IR emitter 202. Consequently, the IR detector 110 receives only the IR signal 604, and thus, during the third time period 1406, the IR detector 110 transitions from its high static state to a low state only when it receives the burst 618. Note that the IR detector 204 receives both IR signals 606 and 608 during all time periods 1402-1406.

The two signals 1402, 1408 are provided by the IR detectors 110, 204 to the system controller 190 for processing. When the signals 1402, 1404 have the beam interruption pattern shown in FIG14, that is, when (1) the signal 1402 indicates that both IR signals 604, 606 are being received by the IR detector 110 during the first time period, (2) the signal 1402 indicates that only the IR signal 606 is being received by the IR detector 110 during the second time period, (3) the signal 1402 indicates that only the IR signal 604 is being received by the IR detector 110 during the third time period, and (4) the signal 1408 indicates that both IR signals 604, 606 are being received by the IR detector 204 during all time periods, the system controller 190 determines that an object or person has traveled through the detector side 208 of the EAS detection zone 150. In some cases, the system controller 190 will take subsequent control measures in response to this determination. The subsequent control measures are the same or similar to those described above with respect to FIG8.

15 , a schematic diagram is provided that can be used to understand the situation where an object or person 1502 is traveling through the center 210 of the EAS detection zone 150. As shown in FIG15 , the object or person 1502 is traveling in the y-direction. Before the person enters the EAS detection zone 150, the two signals output by the IR detectors 110, 204 are the same as those shown in FIG6 .

Note that when both non-adjacent emitters are lost for a short period of time, the beam interruption pattern indicates that a person is traveling in the center of EAS detection zone 150. This will become more apparent as the discussion proceeds. Similarly, when the IR signal transmitted by non-adjacent emitter 108 is blocked at IR detector 204 before the IR signal transmitted by non-adjacent emitter 202 is blocked at IR detector 110, the beam interruption pattern can indicate that an object or person is slightly inside the emitter side of the EAS detection zone. Similarly, when the IR signal transmitted by non-adjacent emitter 202 is blocked at IR detector 110 before the IR signal transmitted by non-adjacent emitter 108 is blocked at IR detector 204, the beam interruption pattern can indicate that an object or person is slightly inside the detector side of the EAS detection zone. This will become more apparent as the discussion proceeds.

As an object or person enters EAS detection zone 150, object or person 1502 first causes a beam break in IR signal 604 transmitted by IR emitter 108, but does not cause a beam break in IR signal 606 transmitted by IR emitter 202. This beam break is detected by IR detector 110, but not by IR detector 204. Indeed, during the time period when object or person 1502 is in first location 1506, IR detector 110 only receives TDM burst 620 from IR emitter 202, thereby detecting the beam break in IR signal 604 transmitted by IR emitter 108. In contrast, IR detector 204 receives TDM bursts 618 and 620 from both IR emitters 108 and 202 during this time period. Note that this detection by IR detector 204 has no impact on this scenario, but must occur before object or person 1502 can reach second location 1508.

If the object or person 1502 continues to enter the EAS detection zone 150, the object or person 1502 will next cause a beam break of the IR signal 604 to be detected by the IR detector 204. At this time, or some time before this time, the IR detector 110 is detecting a beam break of the IR signal 606. When these events occur simultaneously or synchronously with each other during a relatively short period of time, the object or person is considered to be within the center 210 of the EAS detection zone 150.

A diagram 1600 illustrating the signals 1602, 1608 output by the IR detectors 110, 204 in the situation presented in Figure 15 is provided in Figure 16. As shown in Figure 16, both IR signals 604, 606 are received at both IR detectors 110, 204 during a first time period 1602. The first time period is when the object or person 1502 has not yet caused a light beam interruption to occur.

During the second time period 1604, the object or person 1502 is in its first position 1506. As such, a beam interruption occurs with respect to the IR signal 604 transmitted by the IR emitter 108. In effect, the IR detector 110 receives only the IR signal 606 from the IR emitter 202 during the second time period 1604. However, the IR detector 204 continues to receive both IR signals 604 and 606 from the IR emitters 108, 202.

During the third time period 1606, the object or person 1502 is in its second position 1508. As such, a beam interruption occurs for both IR signals 604, 606. Consequently, the IR detector 110 receives only the IR signal 604, and the IR detector 204 receives only the IR signal 606.

The two signals 1602, 1608 are provided by the IR detectors 110, 204 to the system controller 190 for processing. The system controller 190 determines that an object or person is traveling through the center 210 of the EAS detection zone 150 when the signals 1602, 1608 have the beam interruption pattern shown in FIG16, i.e., when (1) the signals 1602, 1608 indicate that both IR signals 604, 606 are being received by the IR detectors 110, 204 during the first time period, (2) the signal 1602 indicates that only the IR signal 606 is being received by the IR detector 110 during the second time period, (3) the signal 1608 indicates that both IR signals 604, 606 are still being received by the IR detector 204 during the second time period, (4) the signal 1602 indicates that only the IR signal 604 is being received by the IR detector 110 during the third time period, and (5) the signal 1608 indicates that only the IR signal 606 is being received by the IR detector 204 during the third time period. In some cases, the system controller 190 will take subsequent control measures in response to this determination. The subsequent control measures may be the same or similar to those described above with respect to FIG.

15-16 . However, if the person is relatively large, the object or person may block different signals at different times than those shown in FIGs. 15-16 . For example, with respect to point (2), if the object or person is relatively large, during the second time period, IR detector 110 may detect the blockage of both IR signals 604 and 606 rather than just IR signal 606. In this case, signal 1602 would indicate that IR detector 110 did not receive the TDM bursts transmitted by either IR transmitter 108 or 202 during the second time period.

17 , a schematic diagram is provided that is useful for understanding the algorithm for determining whether an object or person is located on the emitter side 206 or detector side 208 of the EAS detection zone 150. The timing between changes in the signals output by the IR detectors 110, 204 is used to determine whether the location of the object or person is on the emitter side 206 or detector side 208 of the EAS detection zone 150. By measuring the time difference between the signal changes, the distance of the object or person from a given pedestal 102a or 102b can be estimated. For example, assume that a person 1702 is passing through the detector side 208 of the EAS detection zone 150. In this case, when a relatively small amount of time 1704 exists between (1) the IR detector 110 detecting a first beam interruption of the IR signal 604 emitted by the IR emitter 108 and (2) the IR detector 110 detecting a second beam interruption of the IR signal 606 emitted by the IR emitter 202, the person or object is considered to be relatively close to the pedestal 102b. Conversely, when the amount of time 1706 between the detection of the two beam interruptions by the IR detector 110 is relatively long, the object or person is considered to be relatively far from the base 102b.

In some cases, the algorithm implemented by system controller 190 simply compares the measured time difference 1704 or 1706 to one or more thresholds to determine whether the time difference falls within an expected range for a person traveling through EAS detection zone 150 at a particular distance from pedestal 102b. The algorithm may select the threshold based on the measured speed of the object or person traveling through EAS detection zone 150. In this regard, a sensor 1710 may be placed on each pedestal to detect this speed. Additionally or alternatively, the measured speed may be obtained from an EAS security tag affixed to the object or possessed by the person. In other cases, the algorithm implemented by system controller 190 uses a matrix that roughly correlates time differences with distance from the pedestal, and roughly correlates the time differences with different values depending on the distance between IR detectors 110, 204 and the distance between pedestals 102a, 102b. The beam interruption data from the previous case may also be used in this matrix.

Referring now to FIG. 18 , a flow chart of an exemplary method 1800 for determining where an object or person (e.g., object or person 702 of FIG. 7 , 902 of FIG. 9 , 1102 of FIG. 11 , 1302 of FIG. 13 , or 1502 of FIG. 15 ) is located within an EAS detection zone is provided. Method 1800 begins at step 1802 and proceeds to step 1804. In step 1804, a first infrared signal (e.g., IR signal 604 of FIG. 6 ) is transmitted by a first infrared emitter (e.g., IR emitter 108 of FIG. 1-2 ), and a second infrared signal (e.g., IR signal 606 of FIG. 6 ) is transmitted by a second infrared emitter (e.g., IR emitter 202 of FIG. 2 ). The first infrared emitter and the second infrared emitter are disposed on a first base (e.g., base 102 a of FIG. 1-2 ) of an EAS detection system (e.g., system 100 of FIG. 1-2 ) and are pointed toward an EAS detection zone (e.g., EAS detection zone 150 of FIG. 2 ). In some cases, the first infrared signal includes multiple first signal bursts whose pulse widths differ from the pulse widths of multiple second signal bursts of the second infrared signal. Additionally or alternatively, each of the multiple first signal bursts is transmitted by the first infrared transmitter at a time different from the time at which the second infrared transmitter transmits the second signal burst. As described above, the present invention is not limited to the details of these scenarios. Other signaling techniques employing different modulation frequencies, different wavelengths, different pulse widths, and different data stream transmissions may also be used.

In the next step 1806, during a first time period (e.g., time period 802 of FIG. 8 , 1002 of FIG. 10 , 1202 of FIG. 12 , 1402 of FIG. 14 , or 1602 of FIG. 16 ), a first infrared detector (e.g., IR detector 110 of FIG. 1-2 ) and a second infrared detector (e.g., IR detector 204 of FIG. 2 ) simultaneously detect the first infrared signal and the second infrared signal. The first infrared detector and the second infrared detector are disposed on a second base (e.g., base 102 b of FIG. 1-2 ) of the EAS detection system, pointing toward the EAS detection zone and opposite the first infrared emitter and the second infrared emitter, respectively.

At a later time, it is determined where the object or person is located within the EAS detection zone based on a pattern of signals output by at least one of the first infrared detector and the second infrared detector (e.g., signals 802 of FIG. 8 , 808 of FIG. 8 , 1002 of FIG. 10 , 1008 of FIG. 10 , 1202 of FIG. 12 , 1208 of FIG. 12 , 1402 of FIG. 14 , 1408 of FIG. 14 , 1602 of FIG. 16 , or 1608 of FIG. 16 ), the pattern of the signals reflecting the first infrared signal and the second infrared detector. At least one of the external signals is blocked by an object or person during at least one of the second time period (e.g., time period 804 of FIG. 8 , 1004 of FIG. 10 , 1204 of FIG. 12 , 1404 of FIG. 14 , or 1604 of FIG. 16 ) and the third time period (e.g., time period 806 of FIG. 8 , 1006 of FIG. 10 , 1206 of FIG. 12 , 1406 of FIG. 14 , or 1606 of FIG. 16 ), during which the object or person is traveling through the EAS detection area.

In some cases, when (1) the signal output by the first infrared detector indicates that the first infrared signal is blocked by the object or person during the second time period and the third time period, and (2) the signal output by the second infrared detector indicates that the first infrared signal is blocked by the object or person during the third time period but not blocked during the second time period, the object or person is determined to be in the area closest to the first infrared emitter and the second infrared emitter in the multiple EAS detection zones. Alternatively or additionally, when (1) the signal output by the first infrared detector indicates that the first infrared signal is blocked by the object or person during the second time period but not blocked during the third time period, and (2) the signal output by the second infrared detector indicates that the first infrared signal is blocked by the object or person during the third time period but not blocked during the second time period, the object or person is determined to be in the area closest to the first infrared emitter and the second infrared emitter in the multiple EAS detection zones.

In those or other cases, when (1) the signal output by the first infrared detector indicates that the first infrared signal is blocked by the object or person during the second time period and the third time period, and the second infrared signal is blocked by the object or person during the third time period but not blocked during the second time period, and (2) the signal output by the second infrared detector indicates that both the first infrared signal and the second infrared signal are not blocked by the object or person during the second time period and the third time period, the object or person is determined to be in the area closest to the first infrared detector and the second infrared detector in the multiple EAS detection zones. Alternatively or additionally, when (1) the signal output by the first infrared detector indicates that the first infrared signal is blocked by the object or person during the second time period, and the third infrared signal is blocked by the object or person during the third time period, and (2) the signal output by the second infrared detector indicates that both the first infrared signal and the second infrared signal are not blocked by the object or person during the second time period and the third time period, the object or person is determined to be in the area closest to the first infrared detector and the second infrared detector in the multiple EAS detection zones.

In those or additional cases, when (1) the signal output by the first infrared detector indicates that the first infrared signal was blocked by the object or person during the second time period but not blocked during the third time period, and the third infrared signal was blocked by the object or person during the third time period but not blocked during the second time period; and (2) the signal output by the second infrared detector indicates that the first infrared signal was blocked by the object or person during the third time period but not blocked during the second time period, the object or person is determined to be within the central area of the EAS detection area. The location of the object or person within the EAS detection area can also be determined based on a timing difference between signal changes in the signals output by at least one of the first infrared detector and the second infrared detector.

Upon completion of step 1808, step 1810 is executed. In step 1810, a system controller (e.g., system controller 190 of FIG. 2 ) optionally controls the operation of the EAS detection system based on the results of the determination made in the previous step 1808. For example, the system controller may execute actions to appropriately alert the correct pedestals of the EAS detection system. When a person with an active security tag walks through the EAS detection area, both pedestals will detect the presence of the active security tag. In conventional EAS detection systems, both pedestals will issue visual and/or audible alarms. This may be undesirable in certain situations. Therefore, in the present invention, the system controller determines, based on the signals output by the infrared detectors, whether the person is walking through the transmitter side, the center side, or the detector side of the EAS detection area. Based on the results of this determination, the system controller will execute actions to cause one or more alarms to be issued only for the pedestal closest to the person. As a result, the EAS detection system of the present invention provides a clear indication to the store clerk: (1) which area within the EAS detection zone the person is walking through, and/or (2) which of multiple adjacent EAS detection zones the person is walking through. In effect, the store clerk can make a more informed decision about which of multiple people traveling through one or more EAS detection zones actually possesses an active security tag.

Additionally or alternatively, the system controller can use the results of the above determination to dynamically modify (e.g., reduce) the strength of the antenna radiation field of the pedestal. This dynamic modification has certain advantages, such as saving battery power. For example, if the determination result indicates that a person is traveling through the transmitter side of the EAS detection area, the strength of the antenna radiation field emitted by a particular pedestal is dynamically reduced. Similarly, if the determination result indicates that a person is traveling through the detector side of the EAS detection area, the strength of the antenna radiation field emitted by the particular pedestal is dynamically reduced. If the determination result indicates that a person is traveling through the center of the EAS detection area, the strength of the antenna radiation field emitted by the pedestal is changed.

The system controller can also use this determination to prevent an alarm from being issued if certain conditions are met. For example, consider a first scenario: both pedestals detect a security tag in their vicinity, but the IR detector's output signals indicate that a person is not within the EAS detection zone. In this case, issuing a pedestal alarm is prevented because the person is likely behind the pedestals. Now consider a second scenario: both pedestals detect a security tag in their vicinity, but the IR detector's output signals indicate that a person is entering the facility. In this case, issuing a pedestal alarm is also prevented because an alarm only needs to be issued for people leaving the facility. The present invention is not limited to the details of these two examples.

Although the present invention has been illustrated and described with respect to one or more implementations, those skilled in the art will recognize equivalent alternatives and modifications after reading and understanding this specification and the accompanying drawings. In addition, although a particular feature of the present invention may be disclosed only with respect to one of several implementations, this feature may be combined with one or more other features of other implementations, which may be desirable and advantageous for any given or specific application. Therefore, the breadth and scope of the present invention should not be limited by any of the embodiments described above. On the contrary, the scope of the present invention should be defined in accordance with the following claims and their equivalents.

Claims (20)

1. A method for determining the location of an object or person within an Electronic Article Surveillance (EAS) detection area, characterized in that the method comprises: A first signal is transmitted synchronously by a first transmitter and a second signal is transmitted synchronously by a second transmitter, wherein the first transmitter and the second transmitter are positioned to point towards the EAS detection area; During a first time period, the first signal and the second signal are detected simultaneously by each of the first detector and the second detector, wherein the first detector and the second detector are positioned to point toward the EAS detection area and are located opposite the first transmitter and the second transmitter, respectively; The location of the object or person within the EAS detection area is determined based on a pattern of signals output by at least one of the first and second detectors, the pattern reflecting that at least one of the first and second signals is blocked by the object or person during at least one time period in a second and a third time period, during which the object or person is moving through the EAS detection area; and The intensity of the antenna radiation field emitted by at least one EAS base is dynamically changed using knowledge of where the object or person is located within the EAS detection area. 2. The method according to claim 1, wherein the first signal comprises a plurality of first signal bursts, the pulse width of which is different from the pulse width of a plurality of second signal bursts of the second signal. 3. The method of claim 2, wherein each of the plurality of first signal bursts is transmitted by the first transmitter at a time different from the time at which the second transmitter transmits the second signal burst. 4. The method of claim 1, wherein the signal output by the first detector changes from a high state to a low state in response to receiving a signal burst transmitted by the first transmitter or the second transmitter. 5. The method according to claim 1, wherein, if (1) The signal output by the first detector indicates that the first signal was blocked by the object or person during the second time period and the third time period, and (2) The signal output by the second detector indicates that the first signal was blocked by the object or person during the third time period, but was not blocked during the second time period. The object or person is then identified as being located within the region closest to the first transmitter and the second transmitter in multiple EAS detection regions. 6. The method according to claim 1, wherein, if (1) The signal output by the first detector indicates that the first signal was blocked by the object or person during the second time period, but was not blocked during the third time period, and (2) The signal output by the second detector indicates that the first signal was blocked by the object or person during the third time period, but was not blocked during the second time period. The object or person is then identified as being located within the region closest to the first transmitter and the second transmitter in multiple EAS detection regions. 7. The method according to claim 1, wherein, if (1) The signal output by the first detector indicates that the first signal was blocked by the object or person during the second time period and the third time period, and the second signal was blocked by the object or person during the third time period but was not blocked during the second time period. (2) The signal output by the second detector indicates that neither the first signal nor the second signal was blocked by the object or person during the second time period and the third time period. The object or person is then identified as being located within the region that is closest to the first detector and the second detector among multiple EAS detection regions. 8. The method according to claim 1, wherein, if (1) The signal output by the first detector indicates that the first signal was blocked by the object or person during the second time period, and the second signal was blocked by the object or person during the third time period, and (2) The signal output by the second detector indicates that neither the first signal nor the second signal was blocked by the object or person during the second time period and the third time period. The object or person is then identified as being located within the region that is closest to the first detector and the second detector among multiple EAS detection regions. 9. The method according to claim 1, wherein, if (1) The signal output by the first detector indicates that the second signal is blocked by the object or person, and (2) The signal output by the second detector simultaneously indicates that the first signal is blocked by the object or person. The object or person is then identified as being located within the central area of the EAS detection area. 10. The method of claim 1, wherein the position of the object or person within a first side or opposite second side of the EAS detection area is determined based on a timing difference between a first beam interruption detected by one of the first and second detectors in the first signal emitted by the first transmitter and a second beam interruption detected by the one of the first and second detectors in the second signal emitted by the second transmitter. 11. An Electronic Article Surveillance (EAS) detection system, characterized in that the EAS detection system comprises: A first base and a second base, wherein an EAS detection area is defined between them; A first transmitter and a second transmitter synchronously transmit a first signal and a second signal, respectively, wherein the first transmitter and the second transmitter are arranged on the first base of the EAS detection system and point towards the EAS detection area; A first detector and a second detector simultaneously detect the first signal and the second signal during a first time period, wherein the first detector and the second detector are arranged on the second base of the EAS detection system, pointing towards the EAS detection area and respectively located opposite the first transmitter and the second transmitter; and Electronic circuits, used for The location of the object or person within the EAS detection area is determined based on a pattern of signals output by at least one of the first and second detectors, the pattern reflecting that at least one of the first and second signals is blocked by the object or person during at least one time period in a second and a third time period, during which the object or person is moving through the EAS detection area; and The intensity of the antenna radiation field emitted by at least one EAS base is dynamically changed using knowledge of where the object or person is located within the EAS detection area. 12. The EAS detection system according to claim 11, wherein the first signal comprises a plurality of first signal bursts, the pulse width of which is different from the pulse width of the plurality of second signal bursts of the second signal. 13. The EAS detection system of claim 12, wherein each of the plurality of first signal bursts is transmitted by the first transmitter at a time different from the time at which the second transmitter transmits the second signal burst. 14. The EAS detection system of claim 11, wherein the signal output by the first detector changes from a high state to a low state in response to receiving a signal burst transmitted by the first transmitter or the second transmitter. 15. The EAS detection system according to claim 11, wherein, if (1) The signal output by the first detector indicates that the first signal was blocked by the object or person during the second time period and the third time period, and (2) The signal output by the second detector indicates that the first signal was blocked by the object or person during the third time period, but was not blocked during the second time period. The object or person is then identified as being located within the region closest to the first transmitter and the second transmitter in multiple EAS detection regions. 16. The EAS detection system according to claim 11, wherein, if (1) The signal output by the first detector indicates that the first signal was blocked by the object or person during the second time period, but was not blocked during the third time period, and (2) The signal output by the second detector indicates that the first signal was blocked by the object or person during the third time period, but was not blocked during the second time period. The object or person is then identified as being located within the region closest to the first transmitter and the second transmitter in multiple EAS detection regions. 17. The EAS detection system according to claim 11, wherein, if (1) The signal output by the first detector indicates that the first signal was blocked by the object or person during the second time period and the third time period, and the second signal was blocked by the object or person during the third time period but was not blocked during the second time period. (2) The signal output by the second detector indicates that neither the first signal nor the second signal was blocked by the object or person during the second time period and the third time period. The object or person is then identified as being located within the region that is closest to the first detector and the second detector among multiple EAS detection regions. 18. The EAS detection system according to claim 11, wherein, if (1) The signal output by the first detector indicates that the first signal was blocked by the object or person during the second time period, and the second signal was blocked by the object or person during the third time period, and (2) The signal output by the second detector indicates that neither the first signal nor the second signal was blocked by the object or person during the second time period and the third time period. The object or person is then identified as being located within the region that is closest to the first detector and the second detector among multiple EAS detection regions. 19. The EAS detection system according to claim 11, wherein, if (1) The signal output by the first detector indicates that the second signal is blocked by the object or person, and (2) The signal output by the second detector simultaneously indicates that the first signal is blocked by the object or person. The object or person is then identified as being located within the central area of the EAS detection area. 20. An Electronic Article Surveillance (EAS) detection system, characterized in that the EAS detection system comprises: At least the first base defines the EAS detection area; A first transmitter and a second transmitter, which synchronously transmit a first signal and a second signal respectively, wherein the first transmitter and the second transmitter are positioned to point towards the EAS detection area; A first detector and a second detector simultaneously detect the first signal and the second signal during a first time period, wherein the first detector and the second detector are positioned to point towards the EAS detection area and are respectively located opposite the first transmitter and the second transmitter; Electronic circuitry is used to determine which part of the EAS detection area the object or person is located in based on the following: (1) A pattern of signals output by at least one of the first detector and the second detector, the pattern reflecting that at least one of the first signal and the second signal is blocked by the object or person during at least one time period of a second time period and a third time period, during which the object or person is moving through the EAS detection area; and (2) The timing difference between the first beam interruption detected by one of the first detector and the second detector in the first signal emitted by the first transmitter and the second beam interruption detected by the other of the first detector and the second detector in the second signal emitted by the second transmitter.